The US Labor Secretary Elaine Chao announced yesterday that new MSHA regulations to control diesel particulate matter (DPM) emissions from coal mining equipment will take effect on May 21. The rule, published in January, was originally scheduled to take effect in March, but was subject to the 60 day review period by the Bush administration.

The coal mine rule establishes an engine emission limit of 2.5 grams DPM per hour. Most underground diesel engines will have to be fitted with particulate filters to comply with the requirement.

In the same announcement, the Secretary Chao said the metal/nonmetal mine rule will be subject to a 45-day stay, pending ongoing discussions with stakeholders. “The Department is in ongoing discussions with the United Steel Workers of America and the National Mining Association regarding the final form of a rule for diesel particulate matter in metal/nonmetal mines,” said Chao.

The rule for metal/nonmetal (i.e., non-coal) mines, published together with the coal mine rule, introduces threshold limit values (TLV) for ambient DPM concentrations. These TLVs are to be phased-in from 400 to 160 µg/m3 over a five year period. Most underground engines would need to be fitted with particulate filters to achieve these exposure levels.